This invention relates to a bone-seeking complex of technetium-99m.
Efforts to find a better gamma-emitting radionuclide for skeletal imaging to replace the long-lived nuclide strontium 85 (half-life 65 days) or inconveniently short-lived fluorine-18 (half-life 1.83 hours) have thus far been restricted mostly to the investigation of radioactive divalent alkaline earth cations, and the trivalent cations of gallium and the lanthanons. The excellent physical characteristics (half-life of 6 hours and monoenergetic gamma emission of 140 KeV with an external photon yield of 90%) of the readily available radionuclide technitium-99m are well-known. By virtue of its optimum half-life and absence of beta emission, technetium-99m can be administered in relatively large doses (10-15 mCi) without exceeding reasonable radiation levels. Until recently, technetium-99m has been used extensively in radioisotopic imaging procedures for almost every major organ in man with the exception of the skeleton.
In our copending application, Ser. No. 195,034 (filed Nov. 2, 1971) there is disclosed a metabolizable, bone-seeking composition comprising a technetium-99m-tin-polyphosphate complex prepared from a polyphosphate having a molecular weight above 300, preferably above 1400.
It was discovered that when solutions of technetium-99m-tin-polyphosphate complex are given intravenously, technetium-99m localizes to a great extent in bone, particularly in diseased or abnormal areas of the skeleton. Excellent visualization of both normal bone and skeletal lesions is observed about 2 hours after administration of the complex. Normal and abnormal skeletal tissue are readily delineated using conventional radioisotope imaging devices such as rectilinear scanners or scintillation cameras.
It is an object of the invention to provide technetium-99m in additional bone-seeking forms suitable for use as skeletal-imaging agents.